Restored nice error reports

lark/common.py

@@ -17,6 +17,8 @@ class UnexpectedToken(ParseError):
             context = ' '.join(['%r(%s)' % (t.value, t.type) for t in seq[index:index+5]])
         except AttributeError:
             context = seq[index:index+5]
+        except TypeError:
+            context = "<no context>"
         message = ("Unexpected token %r at line %s, column %s.\n"
                    "Expected: %s\n"
                    "Context: %s" % (token, self.line, self.column, expected, context))

lark/parsers/lalr_parser.py

@@ -9,8 +9,9 @@ class Parser(object):
                           for rule in analysis.rules}
         self.state = self.analysis.init_state_idx
 
-    def parse(self, stream, set_state=False):    # XXX no set_state
-        stream = iter(stream)
+    def parse(self, seq, set_state=False):
+        i = 0
+        stream = iter(seq)
         states_idx = self.analysis.states_idx
 
         state_stack = [self.analysis.init_state_idx]
@@ -23,7 +24,7 @@ class Parser(object):
             except KeyError:
                 expected = states_idx[state].keys()
 
-                raise UnexpectedToken(token, expected, [], 0)
+                raise UnexpectedToken(token, expected, seq, i)
 
         def reduce(rule, size):
             if size:
@@ -46,6 +47,7 @@ class Parser(object):
         # Main LALR-parser loop
         try:
             token = next(stream)
+            i += 1
             while True:
                 action, arg = get_action(token.type)
 
@@ -54,6 +56,7 @@ class Parser(object):
                     value_stack.append(token)
                     if set_state: self.state = arg
                     token = next(stream)
+                    i += 1
                 else:
                     reduce(*arg)
         except StopIteration: